1. Field of the Invention
The present invention relates to an image developing apparatus and an image forming apparatus incorporating the image developing apparatus.
2. Related Art
Known as an image forming apparatus, is an apparatus comprising a latent image forming section which forms electrostatic latent images on an image forming device, an image developing apparatus which forms toner images, a transfer unit which transfers the toner images onto paper transfer sheets, a fixing apparatus which fixes the toner images on the paper transfer sheets and a cleaning device, which cleans the image forming device after transferring the images. An image developing apparatus, which is used in the image forming apparatus, transfers the toner carried by a developing sleeve to a developing area provided opposite the image bearing member.
In recent years, trends such as power saving, colorization and high-speed copy-processes etc. have been getting strong movement. In order to save energy, firstly a low softening point developing agent has been used. Further, in regard to the colorization, when developing apparatuses for developing agents of Y (yellow), C (cyan) and k (black) are integrated compactly, heat of friction generated at shaft bearing sections in a small image forming apparatus, heat generated by motors and heat generated between developing agent and a rotating member are easily generated. Further, heat generation by motors, heat generated by friction between developing agent and rotating members are easily generated since the rotating member rotates at a high speed in order to conduct high-speed copy processes. Consequently, developing agents in the image developing apparatus are easily welded to the developing sleeve in the image developing apparatus and degradation of the developing agent easily occurs when temperature rises.
As to overcome of these drawbacks, a technique to prevent temperature-rise by cooling the surface of a developing sleeve by contacted a developing agent-supplying roller exhibiting a cooling function provided in an image developing apparatus is disclosed in Japanese Patent Application Open to Public Inspection 2001-5280. However, problems concerning complications of configuration, which are needed to provide a cooling function to cool the developing agent-supplying roller, and low cooling efficiency since the developing agent-supplying roller indirectly cools the developing roller. Another technique is to radiate heat from the developing sleeve through an electrostatic charging blade, which conducts electrostatic-charges by touching the developing agent on the developing sleeve, is disclosed in Japanese Patent Application Open to Pubic H7-248673. However, problem is that heat of the developing sleeve is more difficult to radiate away than employing an electrostatic charging blade.